This invention relates to a variable spring member and specifically to a variable spring member including alternating layers of compressible and electro-reactive medium to vary spring rate and stiffness.
A spring is a device capable of absorbing energy and is used in many applications from automotive suspension systems to earthquake survivability systems for buildings. A common type of spring is a coil spring that is typically positioned between two members movable relative to each other. Energy transmitted between members is at least partially absorbed by the coil spring in proportion to physical properties of the coil spring. The stiffness of the coil spring is typically a function of material properties and specific configuration of the coil spring. In some instances, varying the stiffness of the coil spring is desirable to control how energy is absorbed.
Electro-reactive mediums are known in the art and are commonly used within shock absorbers to vary a dampening rate of the shock absorber. Electro-reactive mediums change physical properties in the presence of a magnetic field. Proportionally changing the magnitude of the magnetic field provides a range of dampening characteristics. A typical electro-reactive medium comprises a suspension of tiny magnetic particles disposed within a liquid that significantly increases yield sheer strength when exposed to a magnetic field. The magnitude of the magnetic field determines the proportion of the increase in sheer strength for a specific electro-reactive medium. The increase in sheer strength is achieved by the tiny particles within the medium aligning with a magnetic field.
This phenomenon is common to many different mixtures and types of electro-reactive medium. In such systems a magnetic coil is disposed in the flow path of the dampening fluid between two separated chambers. Changes in the magnetic field vary the viscosity of the electro-reactive fluids to change the flow properties between the two chambers and thereby the dampening rate of the shock absorber.
In some applications, it may be desirable to efficiently absorb input energy while at the same time providing varying degrees of spring stiffness. The degree of stiffness that the device must provide is based on externally determined factors such as applied mass linear rotational acceleration of the object or other environmental conditions. The specific application may also require the use of a device that can have a degree of spring stiffness and the rate of change of spring stiffness controlled accurately and rapidly.
Accordingly, it is desirable to develop a variable spring member capable of varying spring stiffness and rate of change of spring stiffness in response to application specific inputs.